This invention relates to predictive maintenance systems and methods, and more particularly to computer-based data collection systems and methods for measuring and collecting vibration data from machines.
Data collection systems and methods are now widely used for measuring and collecting vibration data from machines, for predictive maintenance purposes. Data collection systems typically include two major components: a portable data collector and a host computer. The portable data collector is typically a dedicated instrument to which accelerometers can be coupled, and which stores accelerometer-based vibration data for a machine. An example of a state-of-the-art data collector is the EMONITOR(copyright) dataline(trademark) data collector marketed by Entek Scientific Corporation, assignee of the present application. The EMONITOR(copyright) dataline(trademark) data collector is described in a manual entitled xe2x80x9cEMONITOR(copyright) for Windows EMONITOR(copyright) dataline(trademark) (U.S.) Data Collector User""s Guide, First Edition 1995xe2x80x9d, Manual No. EEW2501A, published by Entek Scientific Corporation, the disclosure of which is incorporated herein by reference.
The host computer is typically a standard PC-based computer which runs predictive maintenance data management and analysis software thereon. The host software allows a user to set up a database to model the machinery for which vibration data is to be obtained. The software allows lists of machines to be set up for data collection. Each list includes a set of measurement parameters that control where and how to take and store a measurement. The host software allows one or more lists to be loaded into the data collector for collection. The user then takes the data collector to a machine to be measured, accesses the measurement parameters for that machine, and collects and stores vibration and other information. After collection, the data is unloaded from the data collector to the host. The host software then allows the data to be analyzed. Reports can be generated, including reports of measurements that exceed alarms. Graphical displays of the data can be produced, including trend, spectrum, frequency trend, time waveform and spectrum map plots.
An example of data management and analysis host software is EMONITOR(copyright) for Windows, which is marketed by Entek Scientific Corporation, the assignee of the present invention. The EMONITOR(copyright) for Windows software is described in a manual entitled xe2x80x9cEMONITOR(copyright) for Windows User""s Guide, Second Edition 1994xe2x80x9d, Manual No. EEW0002B, published by Entek Scientific Corporation, the disclosure of which is incorporated herein by reference.
In state-of-the-art manufacturing environments, the capital investment in machinery can be staggering. Accordingly, there is a great need for predictive maintenance to prevent machine breakdowns and increase reliability. Moreover, with xe2x80x9cjust in timexe2x80x9d manufacturing requirements, predictive maintenance becomes even more critical to eliminate machine down time. Accordingly, there is a great need for data collection systems and methods.
Unfortunately, the high cost of data collection systems is often a barrier to their widespread use. The high cost is in part related to the use of special purpose hardware and software in the data collector. In addition to high cost, the use of special purpose hardware and software limits the flexibility of the data collector and makes it difficult to update and improve the data collector. Although portable computers, laptop computers, pen-based computers, palmtop computers and Personal Digital Assistants (PDA) have become widely available, they have not yet made a significant impact on data collectors. See for example, the publication in Automatic ID News, April 1995, entitled xe2x80x9cBe Ready for Technology Leap at the End of the Century: Three Non-ADC Developments to Springboard Automatic Data Capture Growthxe2x80x9d. See also the publication in Maintenance, January/February 1995, by Billson et al. entitled xe2x80x9cPortable Pen Computersxe2x80x94An Essential Tool for the Mobile Maintenance Engineerxe2x80x9d.
The present invention is a portable, self-contained data collection system for measuring and collecting vibration data from machines. The system includes an accelerometer including a motion sensitive transducer and an accelerometer output. The accelerometer is coupled to a machine to produce an analog signal at the accelerometer output. The system also includes a data acquisition card having an analog input and a digital output. The accelerometer output is electrically coupled to the analog input. As used herein, electrical coupling includes wireless, optical or conventional wire coupling. The data acquisition card samples and digitizes the analog signal to produce a time domain digital signal, i.e. a sampled and digitized series of voltage versus time points, at the digital output. The system also includes a battery-powered portable computer such as a pen-based computer, which includes an expansion slot. The data acquisition card digital output is electrically and mechanically connected to the expansion slot.
The battery-powered portable computer also includes a database having machine identifications and associated measurement parameters. User input means such as a pen allows user selection of a machine identification for measurement. The portable computer also includes signal processing means for processing the time domain digital signal according to the measurement parameters associated with the selected machine identification. Preferably, the signal processing means processes the time domain digital signal to produce a frequency domain digital signal by performing a Fast Fourier Transform (FFT), wavelet or other digital signal processing operations. Finally, the battery-powered portable computer also preferably includes signal analyzing means for analyzing the frequency domain digital signal to produce predictive maintenance information such as spectral distribution. The time domain digital signal can also be analyzed to produce crest factor and other predictive maintenance information.
A data collection system according to the present invention uses a standard portable computer such as a pen-based computer and a standard data acquisition card such as a PCMCIA sound card, to provide portable self-contained hardware for data collection and analysis. The machine database, signal processing means and signal analyzing means are preferably implemented using software modules which execute on the portable computer. The machine database and the signal analyzing software may be provided using EMONITOR(copyright) for Windows or other predictive maintenance software on the portable computer. Signal processing software may be provided by conventional digital signal processing software which provides digital filtering, integration from acceleration to velocity or displacement units, Fast Fourier Transform or other mathematical functions, and averaging. Accordingly, a low cost self-contained data collection system is provided.
It will be understood that since the portable data collection system includes a database, signal processing software and signal analyzing software therein, a host computer connection is not required for operation. Rather, all predictive maintenance operations may be performed using only the portable self-contained data collection system. However, it will also be understood by those having skill in the art that the portable self-contained data collection system can be used as part of a networked data collection system wherein the portable computer includes transmitting means for transmitting at least one of the machine identifications, the measurement parameters, the time domain digital signal, the frequency domain digital signal or the predictive maintenance information to a second computer. The second computer may store this data for distribution to other users and the second computer or other users may also perform one or more of the processing functions of the portable data collector. The transmitting means is preferably wireless, such as a radio frequency (RF) transmitter. However, transmission may also be accomplished by uploading information to another computer using conventional wire communications.
According to another aspect of the present invention, the portable self-contained data collection system also includes a power supply for supplying power to the accelerometer. In particular, conventional portable computers do not provide sufficient power for an accelerometer, which typically requires 24V at 2 mA. According to the invention, an accelerometer power supply electrically and mechanically couples the accelerometer output to the data acquisition card analog input. The accelerometer power supply is preferably responsive to the data acquisition card for supplying power to the accelerometer when the data acquisition card is activated, and for deactivating when the data acquisition card is deactivated.
In particular, the accelerometer power supply includes a power supply housing and an accelerometer battery power supply in the power supply housing which provides sufficient power for an accelerometer. Output means including an output connector electrically and mechanically connects the accelerometer battery power supply to an accelerometer and receives accelerometer signals from the accelerometer. Input means including an input connector electrically and mechanically connects the accelerometer battery power supply to an external device, preferably the analog input of a data acquisition card. The input means receives a control signal from the external device, and also passes the accelerometer signals to the external device. The accelerometer battery power supply is responsive to the control signal, to activate the accelerometer battery power supply to supply battery power for an accelerometer to the output connector. In the absence of the control signal, the accelerometer battery power supply is deactivated. Preferably, the accelerometer battery power supply will pass signals from the output means to the external device in the absence of the control signal, so that non-powered transducers can be used.
When the accelerometer power supply is included, the portable self-contained data collection system includes three hardware components: a portable computer, a data acquisition card and an accelerometer power supply. The portable computer includes a portable computer housing, a portable computer battery power supply within the portable computer housing to supply power to the portable computer, and an expansion slot in the portable computer housing. The data acquisition card is mechanically and electrically coupled to the expansion slot. The accelerometer power supply includes a power supply housing, and an accelerometer battery power supply within the power supply housing which provides sufficient power for an accelerometer. The accelerometer power supply is electrically and mechanically coupled to the data acquisition card and the accelerometer is electrically and mechanically coupled to the accelerometer power supply. The portable computer, data acquisition card and accelerometer power supply may be packaged in a ruggedized carrying case. The portable computer executes software including a database including machine identifications and measurement parameters, signal processing software for processing accelerometer signals and signal analyzing software for analyzing the processed signal to produce predictive maintenance information.
Data collection methods according to the present invention are used for measuring and collecting vibration data from machines, wherein the following steps are all performed in a portable battery-powered computer: A machine identification for measurement is selected. A time domain accelerometer signal is processed according to measurement parameters associated with the selected machine identification to produce a digital signal. The digital signal is analyzed to produce predictive maintenance information. If necessary, the processing step is preceded by the step of sampling and digitizing an analog accelerometer signal to produce the time domain accelerometer signal. The machine identifications, measurements, time domain signal, digital signal and/or predictive maintenance information can be displayed on the portable battery-powered computer. Portable self-contained data collection systems and methods are thereby provided. In addition, this information can be transferred to another computer.